Such mechanical assemblies formed in this way of a carrying part and a carried part constitute components or subassemblies used in the construction of suspension units for automobile vehicles, for example, being operative in this case between the wheels of the automobile vehicle and its bodyshell, for example.
For obvious reasons, impacts and vibrations caused by the road and which would otherwise be transmitted to the bodyshell of an automobile vehicle must be filtered out and elastic blocks, commonly referred to as elastic joints, are usually employed for this purpose, their axis being in practise joined to the bodyshell of the automobile vehicle. To be operative between the bodyshell and the wheels, they are each individually housed in bushes attached to the suspension arms carrying the wheels.
Here a bush of the above kind constitutes one of the parts, for example the carried part, of the mechanical assemblies with which this patent application is concerned.
The other part, here the carrying part, is then a tubular arm body, commonly referred to as a suspension arm.
The problem is to provide a satisfactory joint between the carried part and the carrying part.
For reasons of overall size, in the case of automobile vehicle suspension arms, the portion of the carrying part comprising the housing receiving the carried part must, in addition to having transverse dimensions matching those of the carried part, also, by virtue of limited crushing, be subject to some degree of crimping, followed by some degree of flattening, which causes two opposite wall areas of the carrying part to move toward each other.
The housing to receive the carried part must therefore be formed in a partly crushed portion of the carrying part, the carried part being assembled to the carrying part afterwards by welding or crimping, for example.
Although satisfactory, this approach has its drawbacks.
First of all, the required crimping is a costly operation in itself and it is desirable to be able to dispense with it.
Also, and more importantly, the housing to receive the carried part can usually be formed only by machining, which is detrimental to cost because it requires heavy investment and a skilled operative.
To avoid the above drawbacks, a method for jointing two tubular parts has already been proposed (for example in document GB-A-2 291 382) in which one of the tubular parts, referred to here as the carrying part, is locally crushed to move two opposite wall areas thereof toward each other, the crushing of the carrying part is continued until the two wall areas thereof concerned are at least locally in contact with each other in a mutual facing area, a closed contour hole is cut in the crushed portion of the carrying part, forming a housing to receive the other tubular part, referred to here as the carried part, and the carried part is assembled to the carrying part by means of this housing.
The invention concerns a method of the above kind in which the portion of the carrying part in which a housing for the carried part must be formed is intentionally completely crushed.
The required housing can then advantageously be formed merely by cutting, and therefore in a particularly simple and economic manner, for example also on a press.
However, in a method of the above kind as applied in the document previously cited, despite being totally crushed, the carrying part has a cross section with too low a second moment of area, as a result of which the resistance to torsion and/or flexing of the carrying part is not satisfactory.
A general object of the present invention is an arrangement which avoids the above drawbacks and has other advantages.